1. Field of the Invention
The present invention relates generally to an automated data storage library, and more specifically to a computer architecture including a high-speed local bus having support for expansion slots and the ability to transfer data blocks in parallel.
2. Description of the Related Art
Automated data storage media libraries accessible to host computers outside the library are known. Such a library includes a set of storage bins for housing a collection of peripheral data storage mediums, a set of peripheral data transfer devices for reading and writing data to the media of the storage mediums, and a robotic picker capable of transferring the mediums upon command from the host. Generally, the picker is capable of inserting a data storage medium into, or removing a data storage medium from, a storage bin or a peripheral data transfer device within the library. An automated storage library provides the host processor with economical access to a large amount of data without manual assistance. The library may also be used for backup and archival purposes of data normally stored on the host computer's disk drive.
In order to interface with the host processor and the robotics electronics, the library must have some communications electronics and/or software of its own, i.e. the library typically includes its own custom-designed computer system. The set of wires, paths, or connections for carrying signals throughout a computer system is known as a "bus". Such a bus is divisible along functional lines such that a library computer system may include a data bus, control bus and address bus. A particular set of communication signal protocols is typically used on a bus, depending upon such factors as the computer system components, the configuration of such components, and the bus pathing scheme. Since the protocols and communications within a library are so specialized, the bus schemes of libraries are therefore typically customized to meet the special needs of a library. The addition of a new type of peripheral data transfer device to the library, such as a new high-speed optical disk device, or new type of communications interface, such as fiber optic cable media, typically requires more hardware and/or software to support the addition.
Some prior art libraries communicate internally with a serial interface, such as an RS-232 interface. Serial communications consist of sequential data transfers. On the other hand, parallel communications include multiple data transfers that happen simultaneously. Parallel buses offer far more cost-effective high-speed communications whenever only short distances are involved, such as within the confines of a computer or library. It would therefore be an economical advantage to provide a library with internal parallel communications.
Up to now, a typical library and any peripheral data transfer devices have communicated with the host through a standard interface called the "Small Computer System Interface" or SCSI for short. The SCSI interface is a family of specifications for a bidirectional, peripheral data transfer device bus and command set. The specifications define a high performance interface that distributes data among peripherals independently of a host processor. The specifications include SCSI-1, SCSI-2, and SCSI-3, and all are governed and available from the American National Standards Institute (ANSI).
Generally, a SCSI bus provides a computer system with data transfer device independence within a class of devices, such as disk drives or tape drives. Different devices within a particular class can thus be added to a computer system without major modification of the system hardware or software.
Nevertheless, it is foreseeable that the higher bandwidth of fiber optics media and the interface and communications standards required to support such higher bandwidth communications may soon obsolesce or at least greatly supplement some SCSI standards. Ultra-SCSI is one attempt within the SCSI specification to increase the bandwidth of SCSI, and other interface protocols specifically designed with fiber optic bandwidths are probably also suitable for very high-speed data transport. For example, Fibre Channel is an interface designed to handle the high data transfer rates (currently up to about 100 Megabytes per second (MBps)) possible with fiber optics. Fibre Channel handles both data channel and network communications and may be used to carry data channels that include the SCSI protocol and may also carry network packet protocols including the Internet Protocol (IP) and Asynchronous Transmission Mode (ATM). ATM is a non-synchronous (i.e., not tied to a master clock) protocol that, among other uses, makes the broadband integrated services digital network (B-ISDN) possible. It is used for video on demand, live television, and generally for high-speed data transport for science, industry, and entertainment, and communications over telephone lines. The need to support such high-speed host interfaces and high-speed network interfaces is not typically addressed in libraries of the prior art, and those that have addressed it have done so with economically undesirable solutions.
It is possible to interface with high-speed host communications, including providing a high-speed Fibre Channel interface to a library, by building a proprietary interface including a communications bus. But such a proprietary bus would have to be redesigned if the interface or communications standards change in the future, with inherent economic disadvantages.
A further consideration for libraries is that the era of the stand-alone computer, such as a desktop personal computer (PC), that is not networked with other computers, in either a client/server or peer-to-peer fashion is largely vanishing as industry and educational institutions carry on the migration of stand-alone to local area network, to wide area network, and further progression to use of the Internet to set up institutional wide intranets. Consequently, the demands on servers is greater than ever, and the data access, and data backup requirements are greater than ever before, with no end in sight. Automated data storage libraries must be available to perform both functions, faster and at least as reliably as before while such faster communications increase demands for data by the growing numbers of computer users.
Moreover, such storage libraries will have a need to communicate directly with the network through such network protocols as Ethernet (IEEE 802.3), fast Ethernet (IEEE 802.3u), token ring (IEEE 802.5), and the fiber distributed data interface (FDDI) which is a high-performance fiber optic token ring network. Of course, standards not even in existence today will need to be supported and without the need for the library communications pathway or bus being redesigned.
In view of the above, it would be an advancement in the art to provide a bus in a data storage library that can support high-speed communications without slowing down or bottlenecking the data transfer and which also imparts the capability for support of industry standard cards for expansion purposes, and so the library's communication pathways do not have to be redesigned to support future growth.